人口普查模型

假设a.txt记录人口普查数据：

　　{'name':'北京','population':100}

　　{'name':'天津','population':150}

　　{'name':'上海','population':200}

　　{'name':'深圳','population':250}

　　{'name':'广州','population':300}

统计人口总数，以及各城市人口比例，代码如下：

def population():
    with open('a.txt','r',encoding='utf8') as f:
        for p in f:
            yield p
iter1 = population()
all_population = sum(eval(i)['population'] for i in iter1)
print('总人口：',all_population)
iter2 = population()
for j in iter2:
    name = eval(j)['name']
    population = eval(j)['population']
    percent = str(population/all_population*100)+'%'
    print(name,population,percent)

显示结果如下:

总人口： 1000

北京 100 10.0%

天津 150 15.0%

上海 200 20.0%

深圳 250 25.0%

广州 300 30.0%